In the discussion that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicants expressly reserve the right to demonstrate that such structures and/or methods do not qualify as prior art.
Micro- and nano-machined devices are used in a variety of industries including electronics, optical, telecommunications, data storage, medical, chemicals etc. Conventional micro scale electrochemical deposition or etching has led to advances in sensor technologies, optical display technology, and micro-actuators. A simple example is the micro-device used to inflate an automobile air bag, whereby the bag is filled with nitrogen released from a solid compound, wherein the solid compound is a micro resistor, which is heated by an electric current. In the medical field micron sized patterns, on certain substrates, have been shown to promote the growth of certain cells, a particular application being in tissue engineering.
The main physical attribute of a micro-device is that the scale of its features are measured in microns, that is in millionths of a metre, and that of a nano-device, wherein the scale of the device's features are measured in nano-metres, that is in thousand-millionths of a metre. Owing to their small size, and their often complex geometries, micro- and nano-devices cannot be manufactured by simple mechanical methods such as cutting, sawing, milling, drilling etc. Under the prior art, methods involve the use of photo-lithography to impose the desired pattern on the substrate of the work-piece followed by chemical etching. The work-piece is first coated with a photo resist. It is then exposed to the image of a photographic mask using visible or ultra-violet light. Unexposed photo-resist is then washed off, and the work-piece etched. The remaining photo resist protects the surface from the etchant. Thus the original photo-mask pattern may be reproduced as a machined surface on the work-piece. The technology of photo-lithography is now well refined, particularly because of its extensive application in the semiconductor industry, and it is for this reason that it has been extended to the fabrication of micro- and nano-devices and featured substrates.
These conventional photo-lithographic techniques for the fabrication of micro- and nano-devices have a significant drawback in the complexity of the process, use of materials, and their disposal to the environment. Every work-piece must be coated with photo-resist, exposed under the photo-mask, and washed before etching. Following the etch, the residual photo-resist must be removed.